Project Summary/Abstract This application is being submitted in response to ?NOT-DA-19-003.? There is a critical need to address opioid use, opioid use disorder (OUD), and overdose risk among young adults. In this administrative supplement to R01-DA040488 (PIs: C Latkin, K Tobin), we will apply the network science-based peer mentor and social diffusion approaches that have been refined as part of the parent study ? ?Test, Link, Cure? (TLC) ? to young adults who use opioids. Funds will support the preliminary development and refinement of ?TLC-Young Adults? (TLC-YA). The TLC-YA intervention is an enhancement of TLC that: (1) expands the focus to include opioid- related content, including reduction of overdose risk behaviors and OUD treatment, and (2) tailored to 18-30 year olds who use opioids, via injection or non-injection routes. We will conduct formative research (i.e., focus group interviews and component testing) and a pilot test to guide modifications to the TLC-YA intervention. TLC-YA participants will be recruited by TLC participants, from among their social networks. The TLC-YA intervention will be designed to use minimal resources so that it can be quickly implemented by health departments and community-based organizations (CBOs). The proposed research activities are well-aligned with the NIH HEAL Initiative and address opioid-related behaviors among a high-risk population, i.e., Black young adults in low-income, urban areas.